In recent years, a balloon catheter has been used to improve a lesion area (stenosed site) inside a body lumen of a living body. The balloon catheter normally includes an elongated shaft portion and a balloon. The balloon is normally disposed on a distal side of the shaft portion and is inflatable in a radial direction (i.e., expandable radially outward). The balloon is brought into a deflated state and is moved to reach a target place inside a living body by way of a thin body lumen. Thereafter, the balloon is inflated, thereby enabling the lesion area to be widened.
If the lesion area is forcibly widened, however, smooth muscle cells may proliferate excessively, and new stenosis (restenosis) may develop in the lesion area in some cases. Therefore, a drug eluting balloon (DEB) has recently been used in which an outer surface of the balloon is coated with a drug for restraining the stenosis. If the drug eluting balloon is inflated, the drug contained in the coated outer surface is instantaneously released to the lesion area, thereby enabling the drug to be transferred to a biological tissue. In this manner, the restenosis can be restrained.
It has been found that a morphological form of the drug on the coated surface of the balloon obviously influences the drug released to the lesion area from the surface of the balloon in terms of the releasing capability or the tissue transferability of the drug. In this regard, it becomes important to control the crystalline form or the amorphous form of the drug on the coated surface of the balloon.
Various methods have been proposed for coating the balloon with a drug. For example, U.S. Pat. No. 8,597,720 discloses that while the balloon is rotated, a coating solution containing the drug is supplied to the surface of the balloon, and the coating solution is dried to form a coating layer containing the drug.